GANYMEDES ANASPIDIS (nOV. GEN., NOV. SP,). 169 



rest is dense^ with a clean-drawn boundary towards the 

 interior, and homogeneous except for a few large vacuoles. 



To this stage probably belongs the cyst in fig, 19, stained 

 by Mann's method. The nucleolus is blue, having given up 

 most of its chromatin to the nucleus, which is violet with 

 dark purple grains. 



In fig. 17 we have another state of affairs: The nu- 

 cleolus, now retreated from the surface, seems to be giving 

 off chromatin to the nucleus in the shape of hollow spherules. 

 It is itself formed of a single central vacuole, surrounded by 

 a layer of small ones embedded in a dense chromatic cortex 

 (the lower nucleolus is cut tangentially, and so does not show 

 this condition). The nucleus, apart from the chromatic 

 spherules, appears perfectly homogeneous, with no achro- 

 matic network, and differs also from the nuclei of other 

 stages in being amoebiform, with " pseudopodia " that can 

 be very clearly seen on focussing up and down. 



From what we know of other Gregarines, it is clear that 

 these stages are preliminary to the breakdown of the large 

 trophic nuclear apparatus, and the reconstitution of the 

 idiochromatin to form the gametocyte nucleus. But, as 

 above mentioned, the cysts soon after this pass into the gut 

 and out by the anus, so that their further development 

 must remain for the present unknown. 



Conclusions : Systematic Position. 



Though here more than ever must we lament the absence 

 of spores, it is still possible to draw some fairly definite 

 conclusions. To start with, Ganymedes is not a Polycystid, 

 nor does it belong to any existing family among the Mono- 

 cystids. Thus a new family, the Ganyraedidae, must be 

 created, whose characters will provisionally be those of the 

 genus : these may be here conveniently summarised as 

 follows : 



(1) The possession by the motile form of a special exten- 

 sible organ at the front end, which may serve for fixation 

 to the cells of the host. 



